In printed circuit board technology, a multilayer circuit board comprises several subcomposite panels having printed circuitry and which are laminated to provide a composite board. The printed circuitry comprises circuit lands or pads to which are connected one or more circuit lines. To repair any shorted or open circuits or to make an engineering change, a plunge end mill cutter is used to delete circuit lands only on the top surface of the board. The top surface of the board has a protective coating applied thereto and, as a result, there is no disturbance or delamination of the circuit line or lines connected to the circuit land during its deletion operation.
It has become desirable to make, what is termed in the art, an early net repair which involves changing the circuitry on a subcomposite panel before it is laminated in the process of assemblying a composite multilayer circuit board. This is also done by using a plunge end mill cutter to delete the desired circuit lands on the panel. However, in this case, the subcomposite or internal panel is not provided with a protective coating and, as a result, the circuit line or lines connected to the land being deleted have a tendency to rise or delaminate from the panel during the delete operation which creates an intolerable condition. It became evident that some means was needed to prevent the delamination of circuit line during a delete operation on a sub-composite circuit panel.